The present invention relates to a device and method for treating cardiomyopathies and/or enlarged hearts and more specifically, a device and method for decreasing a heart chamber""s wall tension.
The natural heart, and specifically, the cardiac muscle tissue of the natural heart (e.g., myocardium) can fail for various reasons to a point where the natural heart cannot provide sufficient circulation of blood for a body so that life can be maintained. More specifically, the heart and its chambers can become enlarged for a variety of causes and/or reasons, including viral disease, idiopathic disease, valvular disease (mitral, aortic and/or both), ischemic disease, Chagas"" disease and so forth. As the heart and its chambers enlarge, tension of the walls of the heart""s chambers increase and thus, the heart must develop more wall tensile stress to generate the needed pressure for pumping blood through the circulatory system. As a solution for the enlarged natural heart, attempts have been made in the past to provide a treatment to maintain circulation.
One such approach has been to replace the existing natural heart in a patient with an artificial heart or a ventricular assist device. In artificial hearts and/or assist devices, a particular problem stems from the fact that the materials used for the interior lining of the chambers of an artificial heart are in direct contact with the circulating blood, which can enhance undesirable clotting of the blood, build up of calcium, or otherwise inhibit the blood""s normal function. Hence, thromboembolism and hemolysis could occur with greater ease. Additionally, the lining of an artificial heart or a ventricular assist device can crack, which inhibits performance, even if the crack is at a microscopic level. Moreover, these devices must be powered by a source which can be cumbersome and/or external to the body. Drawbacks have limited use of these devices to applications having too brief a time period to provide a real lasting benefit.
An alternative procedure is to transplant a heard from another human or animal into a patient. The transplant procedure requires removing an existing organ (i.e., the natural heart) for substitution with another organ (i.e., another natural heart) from another human, or potentially, from an animal. Before replacing an existing organ with another, the substitute organ must be xe2x80x9cmatchedxe2x80x9d to the recipient, which can be, at best, difficult and time consuming to accomplish. Furthermore, even if the transplanted organ matches the recipient, a risk exists that the recipient""s body will reject the transplanted organ and attack it as a foreign object. Moreover, the number of potential donor hearts is far less than the number of patients in need of a transplant. Although use of animal hearts would lessen the problem with fewer donors than recipients, there is an enhanced concern with rejection of the animal heart.
In an effort to use the existing natural heart of a patient, other attempts have been made to reduce wall tension of the heart by removing a portion of the heart wall, such as a portion of the left ventricle in a partial left ventriculectomy procedure (the Batista procedure). A wedge-shaped portion of the ventricular muscle has been removed, which extends from the apex to the base of the heart. By reducing the chamber""s volume, and thus its radius, the tension of the chamber""s wall is reduced as well. There are, however, several drawbacks with such a procedure. First, a valve (i.e., the mitral valve) may need to be repaired or replaced depending on the amount of cardiac muscle tissue to be removed. Second, the procedure is invasive and traumatic to the patient. As such, blood loss and bleeding can be substantial during and after the procedure. Moreover, as can be appreciated by those skilled in the industry, the procedure is not reversible.
Another device developed for use with an existing heart for sustaining the circulatory function of a living being and the pumping action of the natural heart is an external bypass system, such as a cardiopulmonary (heart-lung) machine. Typically, bypass systems of this type are complex and large, and, as such, are limited to short term use in an operating room during surgery, or to maintaining the circulation of a patient while awaiting receipt of a transplant heart. The size and complexity effectively prohibit use of bypass systems as a long term solution, as they are rarely even portable devices. Furthermore, long term use of these systems can damage the blood cells and blood borne products, resulting in post surgical complications such as bleeding, thromboembolism function, and increased risk of infection.
Medicines, such as vasodilators, have been used to assist in treating cardiomyopathies. For example, digoxin can increase the contractibility of the heart, and thereby enhances emptying of the chambers during systolic pumping. On the other hand, some medicines, such as beta blocking drugs, which decrease the size of the chamber of the heart, also decrease the contractibility of the heart. Other types of medicines, such as angiotensin-converting enzyme inhibitors (e.g., enalopril) can help reduce the tendency of the heart to dilate under the increased diastolic pressure experienced when the contractibility of the heart muscle decreases. Many of these medicines have side effects, such as excessive lowering of blood pressure, which make them undesirable for long term therapy.
As can be seen, currently available treatments, procedures, medicines, and devices for treating end-stage cardiomyopathies have a number of shortcomings that contribute to the complexity of the procedure or device. The current procedures and therapies can be extremely invasive, only provide a benefit for a brief period of time, or have undesirable side effects which can hamper the heart""s effectiveness. There exists a need in the industry for a device and procedure that can use the existing heart to provide a practical, long-term use device and procedure to reduce wall tension of the heart, and thus improve its pumping efficiency.
It is the object of the present invention to provide a device and method for treating cardiomyopathies that addresses and overcomes the above-mentioned problems and shortcomings in the thoracic medicine art.
It is another object of the present invention to provide a device and method for treating cardiomyopathies that minimizes damage to the coronary circulatory and the endocardium.
It is still a further another object of the present invention to provide a device and method for treating cardiomyopathies that maintains the stroke volume of the heart.
Another object of the present invention is to provide a device and method for treating cardiomyopathies that supports and maintains the competence of the heart valves so that the heart valves can function as intended.
Still another object of the present invention is to provide a device and method that increases the pumping effectiveness of the heart.
Yet another object of the present invention is to provide a device and method for treating cardiomyopathies on a long term basis.
It is yet still an object of the present invention to provide a device and method for treating cardiomyopathies that does not require removal of any portion of an existing natural heart.
Still a further object of the present invention is to provide a device and method for treating dilated cardiomyopathies that directly reduce the effective radius of a chamber of a heart in systole as well as in diastole.
Additional objects, advantages, and other features of the present invention will be set forth and will become apparent to those skilled in the art upon examination of the following, or may be learned with practice of the invention.
To achieve the foregoing and other objects, and in accordance with the purpose herein, the present invention comprises a static device for use with the heart that has a plurality of members configured to be positioned adjacent the epicardial surface of the heart. The members are joined by at least one connector wherein the members are fixed in a spatial or spaced relationship relative to each other such that a portion of the heart wall is displaced inwardly.
The member(s) can be configured in a rectangular shape, and preferably includes an inner surface having a curved configuration. In one embodiment, the device can have first and second member that are positioned in a spaced relationship relative to each other about 180 degrees apart. The first member is configured to be positioned adjacent the anterolateral surface of the chamber, and the second member configured to be positioned adjacent the posteromedial surface of the chamber.
In an alternative embodiment of the device having first, second and third members, the first, second, and third members are positioned in a spaced relationship relative to each other about 120 degrees apart. The first member is configured to be positioned adjacent the anteroseptal portion of the chamber, the second member is configured to be positioned adjacent the posteroseptal portion of the chamber, and a third member is configured to be positioned adjacent the posterolateral portion of the chamber.
The device also may include a pad adjacent the inner surface, and preferably interposed between the member and endocardial surface. The pad can be made of low durometer solid polymer or plastic or, alternatively, the pad could be a gel-filled or fluid-filled cushion.
The connector of the present invention can also include a chord, such as a heavy braided polymer impregnated polyester suture core with a polyester sleeve, or a heavy monofilament polypropylene or an expanded polytetrafluoroethylene (PTFE, such as the brand Gortex(copyright) by W.L. Gore and Co.) suture, which can traverse the heart tissue and/or cavity. The connector of the present invention can also include a generally rigid pin or rod that is configured to be insertable through, and connect with, the members.
In a preferred embodiment, the device of the present invention can include at least one fixation device on the member configured for insertion into the heart. The fixation device can take the form of a pin for penetrating the wall of the heart, or alternatively, a button for positioning adjacent the endocardial surface of the heart and a cord joining the member and the button.
In another alternative embodiment, the device of the present invention can include a generally horseshoe-shaped harness having a first rigid portion configured to be positioned adjacent the anterolateral portion of the chamber, a second rigid portion configured to be positioned adjacent the posteromedial portion of the chamber, and a flexible portion (in a tangent plane) interposed between the first and second portion and configured to be positioned around the apical portion of the heart. A basal connector is configured to be interposed between the first and second rigid portions of the harness, and preferably is configured to be attachable to the annulus of an atrioventricular valve.
In use, the present invention can reduce the wall tension on one of the chambers of the heart. A static brace is affixed to the heart so as to provide the chamber of the heart as at least two contiguous communicating regions, such as sections of truncated ellipsoids, which have a lesser minimum radii than the chamber before restructuring. As such, the brace displaces at least two portions of the chamber wall inwardly from the unrestricted position.